I use my Macbook Pro (Early 2011) daily. I use it for browsing, watching videos, music creation and app development. It is still is able to handle all these tasks quite well; although more recently, I did see an overall drop in system responsiveness. That was easily improved by
- increasing RAM to 16GB from 4GB
- swapping in a 256GB SSD in place of the stock 320GB HDD
I suppose no other computing component has contributed to improving overall system responsiveness in recent years as the SSD has. The difference it makes is quite remarkable - my boot time reduced by a eighth of what it used to take, and all my applications load faster and act snappier.
Sure the RAM helps, but the SSD is in a whole different league.
The source article also makes note of GPU advances, the popularity of XP and 3D integrated circuits as a way to improve transistor packing - a short but interesting read.
I'll just sit and wait for my quantum computer.